Means for retracting the cores from the electromagnets of a magnetic sound recordinghead



J 1951 D. E. ROSS ET AL 2,538,981

MEANS FOR RETRACTING THE CORES FROM THE ELECTROMAGNETS OF A MAGNETIC SOUND RECORDING HEAD Filed April 26, 1947 s Sheets-Sheet 1- Zmnentors Gttorneg.

Jan. 23, 19 E ROSS ET AL 538,981

1 D. PEANS FOR RETRACTING THE CORES FROM THE ELECTROMAGL EI'S OF A MAGNETIC SOUND RECORDING HEAD Filed April 26, 1947 3 SheetsSheec 2 2,538,931 G THE CORES FROM THE ELECTROMAGNETS Jan. 23, 1951 D. E. ROSS ET AL MEANS FOR RETRACTIN OF A MAGNETIC SOUND RECORDING HEAD 5 Sheets-Sheet 3 Filed April 26, 1947 Patented Jan. 23, 1951 UNITED. STATES PATENT. OFFICEI MEANS FOR RETRACTING THEC'ORES FR M 1 THE ELEcrRoMAGNE'rs O A MAGNETIC SOUND RECORDING HEAD Donald Ross," Eagle Rockyand Herman" S.: Heller, Los Angeles, 'Calif.;' said Ross assignor:

to said Heller Application April'26, 1947, Serial No 744,190- 1 13 Claims. i ((31. 179100.2)

This invention relates generally to recording and reproducing equip-mentof the magnetic type,

and more particularly to coil assemblies for use with such equipment in whichthe pole-piecesof the magnet are moved towardor away from a tape when the latter is to be inserted or re-= moved.

In the construction of magnetic recorders sand reproducers making use of a ferromagnetic tape as the recording medium, it is desirable to be'able to replace the tape with a single simple operation. In the copending application of the present inventors, entitled Removable Magazine For- Tape, Serial No. 720,217, filed January 4, 1947-;

a magazine has been disclosed which may he quickly and easily removed from the translating device, and while the present invention is preferably used in combination with this magazineit may be also used with other magazinesand -de vices as will become apparent.

In the recording and reproducing of sound on a magnetic tape, the latter may advantageouslybe enclosed within a guide having openings therein to receive the pole tips of the electromagnets used in the translation of sound. Consequently it is necessary to separate these pole tips from the tape and the guide if the latter are to be inserted and removed without damaging the 1 pole tips. of the pole tips is accomplished simultaneously Preferably this separation'and return I with the release of a locking assembly holding the r magazine in position, and additionally, these two operations should be accomplished by a single operation of the mechanism. It will be realized that the mechanical separation of the pole tips:

may be accomplished in a number of ways; but It practical considerations arise which impose 'addi tional restrictions upon such a separating means.

For example, where the recording is of the mul-' tiple lane type wherein a plurality of laterally disposed lanes are recorded along the length of the tape, the pole tips must be transversely .mov J able across the tape in a predetermined numberof step-s corresponding to the number of lanes,

and the registration of the pole tips with each of these lanes must be very accurately maintained. Nevertheless, the pole tips must .be' instantly w separable regardless of their lateral positionwithuq.

respect to the tape.

It is, therefore, a major object of th s. inven l tion to provide a pole separating means for electromagnets which will simultaneously separate-= a plurality of electromagnet pole tips-for the in a' sertion or removal of a member therebetween.

Another object of the inventionis to providesucha separating meansiwhich mayibe quickly and easily operated by i an inexperienced opera tor with'a minimum of efiortu It is a furtherobject of this invention to pro vide such a device :in which the pole tips are I maintained ina predetermined-position with re- :I Y spectto the carrying-member, even though the latter-may be movable across the width of the tape. 1

Still another object of the invention is to pro-' vide sucha device-which is mechanically simple yet positive in operation;

It is a still further .object to produce Ia device of 'thistype which, whilefhaving'all of the tear tures .mentionedi: above,-mayi-be produced. at a J cost which is lowfhavingregardfor the precision:

of the work which is to be. done.

These and other objects and advantages of the i invention willbecome apparent; from the followi which Figure 1 is a plan view of a'device'herein shown as a magnetic sound translator, making-useof 1 the improved'pole separating mechanism, with i': the type magazine removed and with the locking '1 handle raised to show: the translatingan'd erasing head "and the control head;

Figure '2 is a cross secti'o'nal view through' the upper portion of the device taken at 2--.2 inxFig- Figure 3 is a cross-sectionalview'through one of the pairs of electromagnets in the erasing and translating head, taken at '3'-3 in Figure 1, with-r the locking handle .raised. and the pole tips in" 1 retracted position.

Figure 4 is a view similar to Figure 3 but with. i the locking handle lowered and the'pole' tips in extended or operating position;

Figure 5 is a perspective viewof a portion of a .ing descriptionof a preferred form'thereof', andf:" from the" drawings fillu'strating that form; in' f.

the operating mechanism used'to retr'act and extend the pole tips shown in Figures 3 and 4;

Figure 6 is a horizontal. sectional View taken at 66 in FigureA, and showing the method of supporting a portion of the operating mecha-- nism shown in Figure 5; 1

Figure '7 is a cross-sectional view "through a pair'of electromagnets of the control head,-taken:.:

at 1-1 in Figure il-and showing the locking han dle in raised position; with the :pole tipsxree' tracted;

Figure:8 is a perspective viewof the-pole tip operating mechanism .usedvin conjunction with the electromagnets of the controlhead; landv Figure 9: is an exploded-perspective view of the '7 a handle and locking assembly, showing the operating elements in their retracted position.

Referring now to the drawings and particularly to Figure 1 thereof, the numeral I indicates generally a housing enclosing a motor, an amplifier, controls for these units, and other miscellaneous equipment associated with a sound recording and reproducing device. The upper portion of the housing I!) is closed by a top or cover II through which couplings I2 project to engage corresponding coupling members of a removable magazine (not shown) and on which a slidable bolt I3 is mounted to engage and lock the magazine in position. While it is to be understood that the herein disclosed apparatus may be used in diiferent devices adapted to receive different types of tape-holding means, in the exemplification shown, the apparatus is adapted to be used with a magazine such as that shown in the previously mentioned ccpending application of the present inventors. As disclosed in that application, the magazine (not shown) is provided with a re-entrant section along its rear edge adapted to receive a sound translating and erasing head I4 and a control head I5. The magazine is also preferably furnished with a tape-guiding means, hereinafter described in greater detail, which surrounds and guides the tape in its passage through the translating and control heads I4 and I5.

Mounted on the cover I I, adjacent the sides of the translating and control heads I4 and I5, are a pair of upstanding ears I3 to which an operating handle I! is attached for movement about a horizontal axis. The ears I8 are located near the rear of the translating and recordin heads I4 and I5, and a pair of arms !8 are pivotally attached to the ears and extend to the handle I? so that when the latter is rotated to its lowermost position, the arms I8 assume a horizontal position extending forwardly to a point in front of the heads I4 and I5. When the handle I1 is moved upwardly, the arms I8 swing about their pivotal connections to the vertical position shown in Figures 1 and 2. The heads I4 and I5 are thus surrounded by the arms I8 and handle I! when the latter are in their lowered position, and a cover is mounted between the arms I8 to cooperate with a magnetic shield or enclosure ZI mounted on the top II to enclose the heads and protect them from the influence of external magnetic fields when the handle I1 is lowered.

In order that the slidable bolt I3 ma be operated to release the magazine (not shown) simultaneously with the raising of the handle I'i, the arms I8 are extended away from the handle, beyond the ears I6, and are provided with horizontally extending pins 22 at their free ends to fit within slots 23 of upwardly extending bifurcated members 24, shown in Figures 4 and 9. From these figures it will be seen that a the pins 22 rotate about the pivotal axis of the arms I8, the former will be moved forwardly as the handle IT is raised, and will be moved rearwardly as the handle is lowered.

Rigiclly connected to the bifurcated members 24 is a U-shaped plate 25 which is slidably mounted on the cover II and which has a forwardly extending projection 26 which carries the slidable bolt I3. The base of the U-shaped plate is located forwardly of the translating and control heads I4 and I5, while the arms of the plate extend rearwardly on each side of the heads to connect to the bifurcated members 24. Forward and rearward motion of the pins 22 is thus trans- 4 mitted from the bifurcated member 24 to the slidable plate 25 so that the slidable bolt I3 is moved forwardly when the handle I! is raised to the position shown in Figures 1, 2 and 3, and is moved rearwardly with respect to the housing II) when the handle is lowered, as shown in Figure 4. It is to be understood, of course, that the magazine (not shown) is designed to be locked in place by the rearward movement of the bolt I3, and to be released by the forward movement of the latter.

The translating and erasing head I4 and the control head I5 consist essentially of electromagnets having cores with very narrow pole tips which bear against the magnetic tape to magnetize the latter or to be magnetically affected thereby to produce a signal. The fundamentals of operation of such a system are well known and will not be repeated here. The signal which is magnetically recorded upon the tape may be adapted to operate a loud speaker or any sort of control or indicating equipment desired. It will be realized, of course, that the use of such a system is not restricted to the recording and reproducing of sound, but may be extended to any phenomenon which may be caused to vary the magnetic strength or field intensity of an elec tromagnet.

In order that the operation of the device may be simplified, certain functions, such as the reversal of direction of tape travel, etc., are performed automatically in response to signals recorded on the tape and detected by the control head I5. This head is quite similar to the translating and erasing head I4, but for the sake of clarity, the heads will be separately described, the translating and erasing head being described first. The latter includes a plurality of identical pairs of electromagnets, one of which is shown in cross-section in Figures 3 and 4 and which will now be described.

As shown in these figures, the head I4 includes a pair of electromagnets 33 and 3I having coils 32 and 33, respectively, surrounding magnetic cores 34 and 35, respectively. The electromagnets 3D and SI are mounted within a housing 36 so that their coils 32 and 33 are axially aligned, and in the form shown, the cores are horizontal, parallel to the top I I. A laterally extending vertical slot 31 is formed within the housing 36 between the electromagnets and 3| so that the adjacent ends of the cores 34 and 35 may extend into the slot from opposite sides thereof. A tape having suitable magnetic properties may be inserted in the slot 31, and a tape guide M is preferably used to support and guide the tape during the latters passage through the heads I4 and I5. The guide 4| surrounds the tape 49 and is provided with suitable apertures or slots therein so that the tips of the cores 34 and 35 may bear against the opposite faces of the tape 40, this guide preferably being of the type shown and described in the previously mentioned copending application of the present inventors. In the presently described form of the invention, it will be apparent that the tape 49 moves in a direction perpendicular to the plane of the drawing in its passage between the core members 34 and 35.

In order that the lineal speed of the tape may be kept within practical limits while permitting the accurate recording and reproduction of higher frequencies, it is necessary that the tips of the cores 34 and 35 which bear against the tape be very narrow in the direction of tape travel. However, in order that: a sufficientamount :of tape 1 may be magnetized, it is important that the width of the tips be considerably greaterin the direcapplication of Herman S. Heller, Serial No.-

696,157, filed September. 11, 1946, now Patent No. 2,514,577, for Magnetic Recorder Pole Piece. As disclosed in this application; the cores 34 and 35 include a series of longitudinally extending laminations encased in a non-magnetic shell 42 of non-circular cross section. At one end of the core, the laminations are reduced in number and/or thickness so that pole tips 44 and 45 are formed, having a magnetic portion of Jverynarrowwidth and only slightly reduced height which bears against the tape 45. 'The poletips 44 and 45 arevery accurately. aligned witheach other, and in this way a very high concentration of magnetic flux is produced within a very limited area of the tape 40. necessary that the larger dimension of the pole tip extend transversely across the tape in a di rection perpendicular to the travel of the latter, i

the shells 42 for the cores 34and 35 are preferably formed of a non-circular cross section as mentioned, so that they may be inserted within the electromagnets and 3| only when the pole tips 44 and 45 are properly oriented. This, of

course, requires a correspondingly shaped central recess or aperture within the electromagnets and 3f to receive the cores 34 and 35.

To urge the pole tips 44 and against the tape 45, the opposite ends of the cores 34 and 35 are provided with enlarged. heads 46 and 47 respectively, and springs 50 and 5| are mounted to bear against the housing 36 and the corresponding heads to urge the cores inwardly. It is to be expected, of course, that the pole tips Y44 and 45 will be worn by their constant-rubbing against the tape 45 and hence provision has been made for the replacement of the cores 34 and 35 when the tips become worn. In the presently described embodiment, this has been done by inserting screw-threaded plugs 52 and .53 in the housing 35 so that the plugs are aligned with the cores 34 and 35, and the outer ends of the springs 50 and bear against the corresponding .plugs. The diameter of the plugs 52 and His slightly larger than the heads 46 and 41 so that it is a simple matter to remove the magnetic shielding 2i, unscrew the plugs 52 and 53 and remove the worn cores 34 and 35, replace the latter, and then reassemble the unit.

It will be appreciated that the axial alignment of the pole tips 44 and 45 is a very important consideration, and the permissible tolerances in aligning these tips must be held to a very small amount. The alignment of the pole tips 44 and 45 'willbe determined by the members supporting the cores 34 and 35 and particularly the members supporting the adjacent ends of those cores. While the central portion of the shells encasing the cores 34 and 35 is preferably rectangular, as previously explained, the pole tips 44 and 45 are preferably encased within a housing or shell portion having a circular cross section since this permits the aperture through which they extend to be circular. the housing 35 is provided with adjacent walls 541on opposite sides of the slot 31, and aligned apertures 55 are formed in these walls to receive the adjacent ends of the cores '34 and 35. As-is In the construction illustrated,

sinca as'mentioned, it is located and dimensioned circular'holes than those i of any: otherushapeyand in this. .way' it .is pos- Siblefto' securevvery accurate aalignment'of the 1 pole tips 44 and 45whileretaining the advantages 1 of the non-circular cross-sectional shape of the body of the cores 34 and 35. The opposite ends of the cores 34 and 35 .are supported by plates 55 attached to the housing 35 and acting both" to support the cores and to retain the coils 32 and 33 in their correct locations. The apertures formed in the plates 55 for the reception of the cores 34 and 35 will, of course, be shapedto hold the cores with a minimum of looseness and wobbling, but any excess clearance between the edges of the holes and the corresponding cores will have a much smaller effect upon the alignment of the pole tips 44 and 45 than a corresponding clearance between the apertures 55 and the adjacent ends of the cores.

While the springs 55 and 55 normally urge the cores 34 and 35 toward each other so that the pole tips 44 and 45 bear against opposite surfaces of the tape 45, it is desirable, as mentioned, to be able to separate or retract the pole tips so that they no longer extend into the slot 31 when the tape is to be removed or replaced. This is particularly necessary where the tape 45 is enclosed within a tape guide 4! since movement of the latter into and out of the slot 31 will normally cause it to bear against the ends of the cores 34 and 35 and thereby destroy the accurate alignment of the pole tips 44 and 45. Since the handle i! must be raised to release the'bolt l3 from the magazine (not shown) preparatory to the removal and/0r replacement of the tape 45 and its guide 4!, the operation of the device will be simplified if the same raising of the handle is effective to retract the pole tips 44 and 45 to a position where they are flush with the adjacent surfaces of the walls 54. In order to accomplish this the retracting mechanism now to be described has been developed.

Slidably mounted within the housing 36 is an operating member 50 having a generally T shape with the stem Bl of the T being disposed horizontally, parallel to the axis of the cores 34 and 35. One side 62 of the cross bar of the T extends in a direction generally downward from the stem 6| while the other side 53 of the cross bar extends upwardly from the stem 6! to a point adjacent the outer end of the core 35. While it will become apparent that with very simple modifications the pole tip separating mechanism may be reversed so that the operating member is adjacent the head 45 of the core 34 instead of the head 47 of the core 35, it has been found that very satisfactory results are obtained by having the operating member act directly on the head 47 in the manner now described.

Mounted on the'upper end of the section 63 of the cross bar is an angular member 64, having a generally horizontally extending flange attached to the upper end of the section 53, and having a generally vertically extending flange adapted to 3 fit beneath the head 4?. The vertically extending there are a plurality of electro-magnets and aswell-known, it is much easier. to "form accurately..7 v sociated cores within the translating and. eras-n 7 ing head l4, and the angle member 64 is made of a sufiicient length to engage all of the heads corresponding to the head 41 of the core 35, and simultaneously retract all of them.

To retract the pole tip 44 from the opposite side of the tape 48 simultaneously with the retraction of the pole tip 45 in the manner just described, the free or unattached end of the stem portion SI of the operating member 68 is connected to the head 46 of the core 34 by means of a pivoted lever so that movement of the stem in one direction causes the movement of the core in the opposite direction. As indicated in Figures 8 to 5, the free end of the stem is provided with a notch 5 in its upper surface adapted to receive a pivoted plate 66. The latter extends downwardly into the notch 65 from a pivotally mounted shaft 6'! whose ends are supported by the housing 36, as illustrated in Figure 6. The notch 55 will normally be somewhat wider than the thickness of the plate 55 in order that the latter may rotate freel about a slight angle as the operating member 60 is moved forwardly and rearwardly. A second rotatable plate 68 is attached to the shaft 6'! for rotation therewith, and extends upwardly from the shaft to a point adjacent the core :54 of the electro-magnet 39. As indicated in Figures 3 and 4, the upper rotatable plate 88 may be provided with an offset section to enable it to fit snugly between the head 3E of the core 3 and the wall 56. The spring 53 will normally urge the head 46 toward the tape 58, rotating the upper rotatable plate 68 in a clockwise direction as seen in Figure 3, and urging the lower rotatable plate 66 toward the rear of the housing 5%, thereby urging the operating member in the same direction. It will be noted that the spring 5| likewise urges the angle member 5- 5, and hence the operating member 69, rearwardly, and thus the springs 56 and 5! cooperate to urge the pole tips 44 and 45 toward each other, while simultaneously urging the operating member 69 toward the rear of the housing. The retraction of the pole tips M and 45 may be accomplished by moving the operating member 6 toward the front of the housing, to the right in Figures 3 and 4, thereby moving the angle member 64 to overcome the urging of the spring 5!, and simu taneously pivoting the upper and lower rotatable plates 68 and. GB about their shaft iii in a counterclockwise direction so that the head is moved against the urging of the spring 55, to the left in Figures 3 and 4.

It will be noted that to retract the pole pieces 34 and 55, the operating member 69 is moved forwardly with respect to the housing 18, which is the same direction that the bolt l3 and the slidable plate 25 are moved when the handle I! is moved to the position shown in Figure 3, preparatory to replacing the tape 65. Likewise, to extend the pole tips :14 and 5 so that the latter bear against the tape, the operating member 69 is moved rearwardly, this being in the same direction that the slidable bolt l3 and plate 25 are moved when the handle :7 is lowered to the position shown in Figure 4 to lock the magazine (not shown) in place. The movement of the slidable bolt [3, however, is much greater than the necessary movement of the operating member 35, and hence some form of motion reducing system must be provided if the movement of the slidable plate 25 is to drive the operating member 60. In addition, it will be seen that it is desirable to retract the pole tips i l and 45 immediately upon starting to raise the handle ll,

and similarly they should not be extended to bear against the tape 40 until just before the handle reaches its lowermost position. In this way, there is very little chance that the pole tips 44 and 45 will extend into the slot 3! where they may be hit or moved by the tape guide 4| when the latter is being removed or inserted into the slot. These two conditions indicate the desirability of a lost motion linkage between the slidable plate 25 and the operating member 60, and such a device has been provided.

As indicated in Figure 9, the base of the U-shaped plate 25 is provided with elongated slots 18 whose axes are parallel to the direction of movement of the plate 25. Each slot 10 is adapted to receive a pin H which is mounted on a slidable push-plate 12 mounted beneath the cover plate H. A spacing plate 13 is attached to the cover ll beneath the heads H! and I5, and the rear end of the push-plate 12 is offset from the cover to bear against the lower surface of the spacing plate. The forward end of the push-plate l2 bears against the undersurface of the cover H, and a shoulder 14 is formed by reason of the offset positions of the forward and rear edges of the push-plate. Holes 15 are formed in the shoulder 3 to receive a pair of horizontal guide rods it which are attached to the forward edge of the spacing plate 73, and helical compression springs are placed over the guide rods 16 to bear against the forward edge of the spacing plate 73 and the rear surface of the shoulder 14. The lower ends of the pins H are attached to the portion of the push-plate l2 rearwardly of the shoulder it and forwardly of the spacing plate 13, being held thereto by nuts 18 or other suitable means, and the pins thus move with the pushplate.

When the handle H is raised and the slidable plate 25 is in its most forward position, the pins ll bear against the rear ends of the slot is and the helical springs ll thus urge the push-plate forwardly. However, as the handle ll is rotated to its lowermost position, the slidable plate 25 is moved rearwardly until such time as the forward ends of the slots E0 bear against the pins H and force them and the push-plate I2 rearwardly against the urging of springs Tl. By the correct designing of the various elements, it is possible to cause a sliding movement of the push-plate 12 of approximately 6, whereas the slidable plate 25 moves a distance of /2". It is to be understood, of course, that these distances are b way of example only and have been found most satisfactory for the particular design of sound translating equipment herein described. Furthermore, it will be seen that the push-plate "i2 is moved rearwardly during the last portion of the downward travel of the handle I'I, and is moved forwardly by the springs 7? during the first portion of the upward movement of the handle. Consequently, movement of the push-plate 12 occurs only when the handle I! is substantially in its locked or lowermost position.

To aid in holding the slidable plate 25 to the cover I I, the pins "I! may be provided with heads 35: or other suitable holding means to bear against the upper surface of the slidable plate and thereby hold the latter and the push-plate 12 on opposite sides of the cover. The push-plate 72 may additionally be held to the spacing plate 13 by screw 8| or other suitable means which pass through slots 82 within the push-plate.

Near its rear edge, the push-plate 12 is provided with a pair of slots 83 and 84, of which the in c l slot83 is adapted to receive.thedowersectionaBZ .of .the:;cross bar .of the operating membertfit. 1.".Thesizeand shapeofithe slot .83 issuch-as. to engage. thesection-tzwith a-relatively close fit 1 lwhich'prevents any; material horizontal move- ;ment between the :two, while permittingvertical movement-oi" the latter with respect to, the pushplate.

As previously mentioned; it hasibeen found desirable touse, a plurality I of. laterally displaced lanes or recording areaswithin a single tape in a recordingand reproducing device of. this type, -and a complete translation system nsin gthis principle is shown in the copendingapplication of Herman S..,Ileller, Serial No. 608,734,. filed August 3, l945,'now Patent No. 2,468,198, granted April 26, 1949, ,andentitled Tape Type Sound Recording and, Reproducing Machine. The present invention is intended for use in such a system, and consequently provisionmust be made for shifting the relativeposition of the pole tips -J34and 45 transversely. with respect to the tape 40. In general, it is not practical toshift the position of the tape itself, and consequently the positionof the pole :tips at and 45 is shifted with respect. to the. tape by raising or lowering the head i l. with respect to the tape and thetop ii. This may be accomplished by mounting the housing dtuupon a plate'85 which is carried by the *upperrend of. a verticallyxextending post or col-- umnfld. Thelatter is mounted for vertical movement withrespect to the top H, and its position maybe determined by a ratchet or steppingarrangementsuch. as: that disclosed in the copending application of 1 Herman S. Heller, Serial No. 608,734. Sincethis positioning device forms no pa1't of the present invention, it is not illustrated,

and the lower; end ofethe post. 86 is shown as being ,broken away, it.being';understood that thepost continues on downwardly to the particular form of positioning a paratus used. As the post 86 is moved upwardly;ordownwardly, the pole tips "-44 and 45 will of course. be correspondinglymoved transversely across the tape id. By the proper design, the tips maybe moved across atape-of a any desired width .in-steps .ofany desired size, and in Figures 3 and l it will be'noted that the poletipsat land tEbear against the tape ,40 in 1 an area near .its center, there being other lanes with. which. thetips may be caused to register by movingtthe. post 85, upwardly or downwardly.

Asthehousing 36 israised and lowered with respect to the. top, it will begapparent that the operating memberfii) will be vmoved vertically with. the housing. Since the handle ll may. be raised to. the position shown in Figure 3 when the pole :tipsi id and 45 arealigned with any one of t the various:laterally-displaced lanes on the tape 40, it is important that the pole tips be retracted by the operation of the handle ll regardless of litheir lateral'alignment with the tape.

The need for the slidable fit between the por .tion 62 of theoperating member Eli and the push iplate E2 will now become apparent.

When the operating'memberfitl is rnoved 'rearwardly, to the iileftin Figures 3 and 4, the cores 34 and 35 are ..moved toward each other in the manner previous- -1y. described and the-pole tips it and lii bear ztagainst-opposite faces of the tape 45. Whenthe operating. member 6&3 isrmoved forwardly, to -the .rightin Figures 3- and 4, the pole tips A l and lii are retracted, leaving the slot3l unobstructed so 'rthat thetape id andtape guide ii may be freely -moved therein. The extension and retraction of 'the pole tips stand: 45. will occur. in this manner whenever-the operating memberlit) is moved, re-

,; gardless of the vertical distance of-the, housing extended when the handle is placed in itslcwermost'positiomregardlss of the distance 01. the housing ifiabove the cover 5 I.. It will be realized,

-ofcourse, that all-of thepole tips of the various pairsof electro-magnets within the translating and recording headid will simultaneously belretracted and extended, whether there. are .two,

three, or any other number of pairs of electromagnets within the head.

a As previously mentioned, the presentlyi described apparatus has certain of its functions -.-,contro-lled by signals recorded on the tape,.,40-,-1and hence there isprovided a control head.,.l5 which is illustrated in detail in Figures land 8.. Itwill be noted that the control head i5. is similar in manyrespectsto the translatingand-erasing head it previously described, with the exception that the vertically movable post 86 is omitted, andthe housing 36a, corrsponding to. the housingl36of the translating and erasing head, isfirmly.,attached-to the top i i. For clarity and easeof -un- ,derstanding, theparts shown in Figure 'Z-Which -correspond tothose shown in Figures land 5 have been given the, same reference. numerals with the letter 11 added thereto. Thus; the hous- .:ing 36a encloses a pair of electro-magnets (3.0a -and 3ia consisting of windings 32a.and .33qurespectively, surrounding cores S la and 35a. .'I fhese I within the tape guide 4!.

coreshave pole tips 440- and .l;5a ,which bear against opposite faces of thetape ll] enclosed The. latter .two elements, it willbeappreciated, are thesameelements which appeared in Figures 3. and 4 illustrating= the translating and erasing head, and merely continue through both the heads. [4, and

. E5. The opposite ends of the pole pieces Add and a are provided with heads, 46a and 41a which i are urged toward the tape ilfl by springs 50:; and

5 la. An operating member 68a is mounted within the housing 56a, and is provided with agenerally horizontally extending .sternlportionfila -and a downwardly extending section 62a of a cross bar.

Substantially aligned with thelatter is anupwardly extending section 6311 of the cross bar, provided with an angle Sta at its upper end; The .free end of the stem Eila is provided with a notch a into which fits a pivotedv plate assembly comprising, a pairof plates 56a, and

58a mounted on a shaft 61a. It will be appreciated that-the cores 34a and 35a are similar-to the cores tii andtti of the first describedhead and electro magnets 353a and Sia are so constructed that the pole tips Ma and 15a will beialigned with each other and oriented with respect .to the tape M3 in a manner. similar to thatpre- -,.viou ly described.

However, as previously mentionedthe control head I5 is not intended to be movablectransverselyacrossthe, tapeJlil, and. henceal-l of the 7",. pairs of electro-magnets within, this head must r 11 be permanently aligned with the particular lane with which they are to cooperate. If there are two lanes which are to be used for signal or control purposes, there will normally be one pair of electro-magnets within the control head i for each of these lanes. In addition, since these lanes are laterally displaced with respect to the tape, the pole tips of the corresponding pairs of electro-magnets will likewise be laterally displaced with respect thereto, and consequently one pair of electro-magnets will be further above the top II than the other. Since the pole tips of both pairs of electro-magnets are to be retracted simultaneously, they should both be operated by the angle member 64a and the pivoted plate 68a. Because of the difference in elevation above the top H, however, the cores of one pair of electromagnets will not be aligned with those of the other pair, and consequently it is desirable to notch the angle 64a and the pivoted plate 68a to form recesses 90 and 9 I, respectively, to receive the corresponding cores. These notches 90 and SH are shown in Figure 8, where it is seen that they permit the simultaneous operation of two pairs of laterally displaced cores with a minimum I of parts.

The operation of the operating member 60a, with the exception just noted, is identical with that previously described in connection with the translating and erasing head M, and the operating head I5 is actuated by the engagement of its lower cross bar section 62a which fits into the slot 84 of the push-plate 12. As in the case of the corresponding members of the translating and erasing head 14, the lower cross bar section 62 fits within the slots 84 with a reatively snug fit which nevertheless permits vertical movement of the operating member 6011 with respect to the push-plate 12. While the control head I5 is not intended to be raised and lowered with respect to the top H, for ease in assembly and maintenance it is advisable to have the head and its operating member 60a readily disengageable from the push-plate 12 in case the head must be repaired or replaced.

From the foregoing, it will be seen that a magnetic coil and pole tip assembly has been provided for use in magnetic sound translators, particularly those of the multiple lane type. By a single, simple operation of the handle [7, the tape magazine (not shown) is released and the pole tips are retracted so that the magazine and the tape and guide carried thereby may be easily and quickly removed from the recording and reproducing device. In a similar manner, the reverse movement of the handle locks the magazine in place and extends the pole tips so that they bear against opposite faces of the tape, while assuring that their accurate alignment is maintained at all times. Furthermore, this retraction and extension of the pole tips may be accomplished at any time, without regard to the transverse position of the translating and erasing head I4 with respect to the tape 40.

While a preferred embodiment of this device has been shown, it will be realized that modifications may be made therein without departing from the spirit of the invention as herein defined, and the latter is not to be limited to theparticular construction or arrangement of parts herein described and shown except as covered by the claims.

We claim:

l. A device for retracting the pole tips of a pair of electro-magnets from an element between them, which includes: a core in each of said electro-magnets attached to the corresponding pole tip thereof; an operating member movable in a direction parallel to the desired movement of one of said pole tips; means connecting said operating member to the corresponding core of said pole tip; and pivoted means interconnecting said member and said remaining core whereby movement of said member in one direction moves said remaining core in the opposite direction, thereby separating said pole tips.

2. A device for retracting the pole tips of a pair of electro-magnets from an element between them, which includes: a core in each of said electro-magnets attached to the corresponding pole tip thereof; an operating member movable in a direction parallel to one of said cores; means connecting said operating member to said lastmentioned core, whereby movement of said member in one direction moves said core and its associated pole tip in the same direction; pivoted means interconnecting said member and said remaining core, whereby movement of said member in one direction moves said remaining core and its associated pole tip in the opposite direction, thereby separating said pole tips; and resilient means urging said cores and said pole tips together.

3. A device for retracting the pole tips of a pair of electro-magnets from an element between them, which includes: a movable core in each of said electro-magnets attached to the corresponding poie tip thereof; an operating member movable in a direction parallel to the movement of one of said cores; an enlargement formed on each of said cores; resilient means urging said enlargements and the pole tips associated therewith together, whereby said pole tips bear against said element; means bearing against one of said enlargements and operable to move the pole tip associated therewith away from said element, against the urging of said resilient means, said means being connected to said member for operation thereby; and pivoted means bearing against the other of said enlargements and connected to said member to move the other of said pole tips in the opposite direction, against the urging of said resi.ient means, away from said element, whereby movement of said member in one direction separates said pole tip, and movement in the opposite direction returns said pole tips toward said element.

4. A device for separating the pole tips of a pair of electro-magnets adapted to be moved across an element between them, which includes: a supporting member; a housing mounted on said supporting member and movable with respect thereto; a pair of electromagnets within said housing having cores with adjacent pole tips axially movable relative to said electromagnets and adapted to bear against opposite sides of said element and move with said housing thereacross; an operating member movable in a direction to retract one of said pole tips relative to its electromagnet; means connecting said member to said pole tip to retract the latter; pivoted means interconnecting said member and said remaining pole tip whereby movement of said member in one direction moves said remaining pole tip in the opposite direction relative to its electromagnet, thereby separating said tips without moving said electromagnets; and slidable means mounted on said supporting member for movement in a direction substantially perpendicular to that of said housing, slidably connected movement of said operating member pivots said' a to said-operating member; 'whereby movement of said slidablemember acts to separate said pole tips regardless of the position of said housing. I 5.- A device f r separating- -the pole tips of a pair of electromagnets adapted to be moved across.

an element between them, which includes: a supporting-member; a housing mounted on said supporting member and movable with respect there- 4 to; a pair of electro-magnets within said housing having cores with adjacent pole tips adapted to bear against opposite sides of'said element, said pole tipsbeing movable with said housing across said element;- an operating member mounted within saidhousing for sliding movement in a direction generally parallel to the axes of said cores; an arm attached to said operating member and extending in a direction substantially-parallel to the direction of movement of saidhousing; an

enlarged-head formed an each-'of-said cores;

-' spring means bearing'against said housingand said'heads to urge said cores and-said pole tips toward said element;--means rigidly connected to said operating member and -extending beneath one of'saidheads to urge the latter and its associated'coreaway from saidelement against the Y urging of said spring means; means pivotally attached to said housing, connected to said operating member andsaidhe'ad of the other of said cores to urge the latter away from said element simultaneously with the movement of said firstmentionedcoreaway-from said element; and a member slidably attached to said housing for movement-in a direction substantially parallel to that'of said operating member,- said arm of said operating member being slidaoly connected to saidslidabl member, whereby operation of the latter acts to separate said pole tips regardless of the position of said housing.

6. A device for retracting the pole tip of a pair of electro-nagnets from an element between them, which includes: a housing adapted to receive said element; a pair of substantially co-axial electro-magnets mounted-within said housing,

each of'said electro-magnets having an axially slidable core, the adjacent pole tips of said cores being adapted to bear against opposite sides of said element; an enlarged head formed on each of the remote ends of said cores; aspring extending between each of said heads and said housing to urge said cores toward said element; a T- shaped operating-member slidably mounted in said housing'with its stem generally parallel to the axes of said electre-magnets and its crossbar perpendicular thereto; rigid plate means on said cross bar extending beneath said head of one of said cores, movable with said operating member to move said core against the urging of said spring, away from said element; and plate means pivotally attached tosaidhousing for rotation about anaxis generallyperpendicular to said axis of electrc-magnets, with one end of said plate means fitting into a notch in said stem of said operating member, and the other end fitting beh head ofthe other of said cores, whereby plate means to move said last-mentioned core, against the urging of said spring, away from said element at the same time said first-mentioned core is moved away therefrom.

7. A device for separating the pole tips of a pair of eleetro-magnets adapted to be moved acrcss'an element between them, which includes: asupporting member; a h'ousing mounted on said supporting member and movable with-=respect thereto adapted to receive said element; a pair of substantially co-axial nelectro-magnetszmonnted within .said housing and .movable therewith, each of said electro-magnets having an. axially slidablecore, theadjacentpole tips: of said'icores being adapted to bear against opposite sides'of said. element; an enlarged head. formedon each of .the remote ends'ofsaidicores; a spring extend- 1 1': ing'betWeen-each of said'headsand said housing .to urge: said cores: toward said element; a -T- .shapedoperating .member slidably mounted in said housing formovement along its axis of symmetry with its stem generally parallel to the axes of said electro-magnets and its cross bar pervpendicular thereto; plate means on'=said crossbar iextending beneath said-head of..one:of said cores,

movable with saidoperating member to move said move said last-mentioned core; against the urging ofrsaidz': spring; away from said .elementat the same". time said..;firstmentioned core' is moved therefrom; and a member'slidably attached to saidhousing for movementzin a direction sub- Tstantially parallel to that of'said operating. memher; said tstemtcf operating'me'mber being slidably connected to said; slidable .member,

whereby :operaticn of. the latter acts to .separate said pole .tips' regardless. of the "position of said housing.

8. A device for-retracting the pole tips of a pair of electromagnets froman element'between them, which includes: a supporting member; a

handlepivotally attached" to. said support; a plate slidably mounted on said support; an ear on said plate. having a bifurcated end adjacent i said handle; a projection on said handle engagingsaid bifurcated ear, whereby rotation of said handle slides said plate along said support;

- a housing adapted to receive said element; a pair 0f electro-magnets within said housing, having :core members with pole tips adapted to bear against opposite sides of. said element; an operatingrnember actuated by said slidable plate for 1 movement in a direction to retract one of said pole tips; means connecting said operating memher to one of said pole tips to retract the latter; and pivoted means interconnecting said member and said remaining pole topwhereby movement of said operating member in one direction moves said remaining pole tip in the opposite direction,

" thereby separating said pole tips.

9.- Adevice for retracting the pole tips of a pair of electro-magn-ets from an element between theinfwhich includes: a supporting member; a

handle'pivotally attached to saidsupport for "movement in a plane perpendicular to the surface thereof; a plate slidably attached to said support for movement in a planesubstantially parallel'to said surface; thereof; a bifurcated ear "attached to said plate;extending-perpendicular thereto adjacent said-"handle; aprojection on a said handle rotatable therewith, and'extending into saidibifurcated ear to move the latter and -saidslidable' plate; a housing adapted to receive :saidelement; 'apair of substantially coaxial electro-rnagnets mounted within said housing-,each *ofsaid electromagnets'having-an axially slidable core; the "adjacent pole tips otsaid: cores being adapted to bear against opposite sides of said element; an enlarged head formed on each of the remote ends of said cores; a spring extending between each of said heads and said housing to urge said cores toward said element; a T-shaped operating member slidably mounted in said housing with its stem generally parallel to the axes of said electro-magnets and its cross bar perpendicular thereto and connected to said slidable plate for operation thereby; rigid plate means on said cross bar extendin beneath said head of one of said cores, movable with said operating member to move said core, against the urging of said spring, away from said element; plate means pivotally attached to said housing for rotation about an axis generally perpendicular to said axes of said electro-magnets, with one end of said plate means fitting into a notch in said stem of said operating member, and the other end fitting beneath said head of the other of said cores, whereby movement of said handle moves said operating member to pivot said plate means and move said last-mentioned core, against the urging of said spring, away from said element at the same time said first-mentioned core is moved away therefrom.

10. A device for simultaneously retracting the pole tips of a pair of electro-magnets adapted to be moved across an element between them, and a pair of electro-magnets which are immovable across said element, which includes: a supporting member; an actuating member movably attached to said supporting member; a movable housing mounted on said supporting member for movement across said element; a pair of electromagnets mounted within said movable housing for movement therewith, said electro-magnets having core members with pole tips axially movable through said electro-magnets and adapted to bear against said element; operating means mounted in said movable housing for movement therewith in one direction, and movable in a substantially perpendicular direction to separate said pole tips, said operating means being connected to said actuating member for sliding movement with respect thereto in said first direction; a housing fixed to said supporting m mber; a pair of electro-magnets mounted within said housing, having core members with pole tips axially movable therethrough and adapted to bear against said element; and operating means mounted in said fixed housing to separate said last-mentioned pole tins, and connected to said actuating member, whereby operation of said actuating member simultaneously separates both of said pairs of pole tips from said element, regardless of the position of said movable housing.

11. A device for simultaneously retracting the pole tips of a pair of electro-magnets adapted to be moved across an el ment between them, and a pair of electro-magnets which are immovable across said element, which includes: a supporting member; a handle pivotally attached to said support; a plate slidably mounted on said support; an ear on said plate having a bifurcated end adjacent said handle; a projection on said handle engaging said bifurcated ear, whereby rotation of said handle slides said plate along said support; a movable housing adapted to receive said element and be moved thereacross; a pair of electromagnets within said housing and movable therewith, having core members with pole tips adapted to bear against opposite sides of said element; an operating member within said housing and movable therewith, connected to said slidable plate for sliding movement with respect thereto in a direction substantially perpendicular to said movement of said plate; means connecting said operating member to one of said pole tips to retract the latter; pivoted means interconnecting said member and said remaining pole tip whereby movement of said operating member in one direction moves said remaining pole tip in the opposite direction, thereby separating said pole tips; a housing fixed to said supporting plate and adapted to receive said element; a pair of electro-magnets within said fixed housing, havin core members with pole tips adapted to bear against opposite sides of said element; an operating member within said fixed housing and connected to said slidable plate; means connecting said last-mentioned operating member to one of said last-mentioned pole tips to retract the latter; and pivoted means interconnecting said lastmentioned operating member and the other of said last-mentioned pole tips whereby movement of said operating member moves said last-mentioned pole tip in the opposite direction, thereby separating said last-mentioned pole tips.

12. In a magnetic recording and/or reproducing machine, the combination of: a housing, a pair of substantially co-axial electromagnets mounted in said housing at a fixed axial spacing distance, there being a pasageway through said housing between said electromagnets for passage of a linear magnetic recording element, axially slidable cores in said electromagnets adapted to bear on opposite faces of said recording element, spring means urging said cores into tight pressural engagement with said record element, core retraction means movable in a given direction to retract said cores, operative connections between said means and said cores causing said cores to be simultaneously retracted by virtue of a given movement of said means, spring means urging said core retraction means toward a position wherein it retracts said cores, and operating means for said core retraction means having a lost motion operative connection with said core retraction means.

13. A combination as defined in claim 12, wherein said housing for said electromagnets is movable in a transverse direction relative to the linear recording element, and wherein said core retraction means includes a first portion movable with said housing and operatively connected with said cores, and a second portion connected to said operating means movable by the latter through said lost motion connection in a direc tion at right angles to the movement of said housing, said first portion of said retraction means having a sliding operative engagement with said second portion of said retraction means.

DONALD E. ROSS. HERMAN S. HELLER.

REFERENCES CITED Country Date Australia Dec. 23, 1937 Germany July 21. 1936 Number Number 

